At present, approximately 50% of U.S. children need orthodontic treatment and 35-40% now receive it in many areas. Of these, nearly half are treated for Class II malocclusion, which is characterized by a relative protrusion of the upper incisor teeth but most frequently is caused by an underdevelopment of the lower jaw during growth. The goal of this project is to compare three alternative treatment approaches to skeletal Class II malocclusion (i.e., Class II malocclusion due to a discrepancy in jaw growth): early orthodontic treatment to modify the growth of the jaws prior to adolescence; late orthodontic treatment to reposition the teeth and compensate for any jaw discrepancy, usually done during adolescence; and surgical-orthodontic treatment to reposition the jaw(s), which typically is reserved for severe problems in late adolescents or young adults. Ideally, we would do this entirely in a randomized clinical trial (RCT), but time constraints make it impossible to use only this method in an initial granting period. Therefore, we will begin a RCT to study early versus late orthodontic treatment, to assess the extent to which growth modification occurs with headgear and/or functional appliance treatment, and to assess the impact of early treatment on oral health. We also will utilize an observational study with retrospective and prospective data for two purposes: (1) to obtain preliminary data comparing these treatment methods and (2) to compare late orthodontic versus orthodontic-surgical treatment of the more severe problems. Our focus will be on the morphologic treatment effects, number of patients in whom treatment goals were reached and percent improvement, impact on oral health, and degree of patient satisfaction as indicated by utility functions. We will investigate the potential usefulness of decision analysis techniques to determine the perferred treatment approach under given conditions and will attempt to identify the critical factors in such a decision. A significant improvement in the quality of orthodontic treatment could be achieved by a demonstration that one of the treatment approaches was superior in specific circumstances.